InfoSec Handlers Diary Blog

Fellow ISC Handler Tom Liston already covered the emergence of hacked DNS zones ("What's In A Name") a couple weeks ago. Back then, the majority of the sites that we found affected by the problem were used to peddle porn and enhancement pills. Not so anymore - the current round of hacked zone files now leads to malware. [Yes, malware. So if you go investigating any of the hostile sites mentioned here on your own .. don't blame us for what happens to your computer]

The domains affected have been abused for the past several days to push copies of the BlackHole Exploit Kit. The IP range used changes about every three, four days:

188.247.135.37 in use until Dec 2, AS34714, Opticnet, Romania
146.185.245.72 in use until Dec 5, AS43215, Monyson Group, Russia
91.196.216.50 in use since Dec 6, AS43239, Spetsenergo, Russia

One of the many exploits launched by these sites is for the Java Vulnerability CVE2011-3544 (RhinoScript Engine)

Note how the exploit code politely checks which version of Java is present, and only launches the exploit on Java installations that are not running the very latest update. Unfortunately, this seems to be the case for the majority of Java deployments out there. Today, almost two weeks after this latest wave of exploits started, the exploit code for CVE2011-3544 is still only detected by roughly half the anti-virus companies on VirusTotal .

Also note the encoded parameter passed to the Java applet (param name='p' value='e00..'). This passes the URL of the next stage executable to the applet, and specifies which EXE the applet should download and run once the exploit is successful. The URL is encoded with a mechanism that uses a lookup table to map between encoded and cleartext characters, but can be reversed by looking at the (heavily obfuscated) source code of v1.class.

The file names "v1.jar" and "v1.class" have been used by this exploit kit for a couple days now. In case you are wondering about infections in your company and you have a decent proxy log, searching for downloads of v1.jar, followed by a later download of an executable .. well, will tell you that you've been had. (Not finding anything is though no guarantee of course that you have NOT been had .. there are several other file names in use by the exploit).

While the Java exploit for CVE2011-3544 isn't the only one in the kit, it is likely by far the most successful for the bad guys at the moment. Considering the malware mess that Java vulnerabilities have caused for PC users in the past several months, any continued advice to "patch it" seems cynical at best. If you have to keep it installed, by all means, patch it. But if you can get away with it, the better option is to throw Java off your computer completely. Chances are high you won't miss it.